Melt chocolate in top of a double boiler over hot water; cool to lukewarm. Separate eggs and put egg whites into a medium size bowl, put the yolks in a small bowl for the time being. Beat egg whites until foamy white and double in volume. Beat in 1/4 cup of sugar, 1 tablespoon at a time until meringue stands in soft peaks. In a large bowl, beat butter and the other 1/4 cup of sugar until mixture is well blended. Beat in the egg yolks until smooth, then the cooled chocolate. Sift flour and salt into chocolate mixture; stir to blend and add vanilla. Stir 1/3 of the meringue mixture into the chocolate mixture, fold in the rest of the meringue until blended. Spread into a Buttered 15 x 10 x 1 inch baking pan; lined with buttered wax paper. Bake at 350 degrees F. until top of cake springs back when lightly touched (about 15 minutes). Cool in pan for 5 minutes; loosen cake around edges of pan with a sharp knife; invert cake onto a large cookie sheet; peel off wax paper; invert onto cooling rack and let cool.

Cut chocolate into small pieces, combine with cream and sugar in a saucepan. Heat slowly, stirring constantly, until chocolate melts; remove from heat and stir in vanilla and coffee. Pour into a bowl and chill until completely cold (usually about 1 1/2 hours). Beat chilled chocolate cream mixture until stiff and thick.

Cut cooled cake in half crosswise. Place 1 half on a small cookie sheet. Spread filling in a layer about 1 1/2 inches thick on top. Place the other half of cake on top of the filling. Chill until filling is firm (about an hour).

In a saucepan, heat sugar and coffee until sugar dissolves. Cut chocolate into small pieces and add to saucepan along with the corn syrup. Bring to a slow (lightly bubbling) boil and cook stirring constantly for 5 minutes. Remove from heat add butter and vanilla. Beat until mixture begins to thicken (about 5 minutes). Quickly spread over chilled cake about 1/4 inch thick. Chill for at least 1 hour.